Method and apparatus for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio. A reference level is determined, above which at least a portion of the magnitude of an input signal being a modulated signal that is input to the power amplifier, or a baseband waveform that is used to generate the modulated signal, is defined as an excess input signal. The magnitude of the input signal is continuously sampled, for detecting an excess input signal. A lower level of operating voltage is supplied to the power amplifier, if no excess input signal is detected. The lower level of operating voltage is sufficient to effectively amplify input signals having a magnitude below the reference level. A higher level of operating voltage is supplied to the power amplifier, whenever an excess input signal is detected. The higher level of operating voltage is sufficient to effectively amplify input signals having a magnitude above the reference level.

Patent
   6437641
Priority
Mar 10 2000
Filed
Sep 26 2000
Issued
Aug 20 2002
Expiry
Sep 26 2020
Assg.orig
Entity
Large
59
12
all paid
1. A method for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio, comprising:
a) determining a reference level, above which at least a portion of the magnitude of an input signal being a modulated signal that is input to said power amplifier, or a baseband waveform that is used to generate said modulated signal, is defined as an excess input signal;
b) continuously sampling said magnitude of said input signal, for detecting an excess input signal;
c) if no excess input signal is detected, supplying a lower level of operating voltage to said power amplifier, said lower level of operating voltage being essentially constant and sufficient to effectively amplify input signals having a magnitude below said reference level; and
d) whenever an excess input signal is detected, supplying a higher level of operating voltage to said power amplifier, said higher level of operating voltage essentially tracks the magnitude of said excess input signal, thereby being sufficient to effectively amplify input signals having a magnitude above said reference level.
11. Apparatus for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio, comprising:
a) a sampling circuit for continuously sampling the magnitude of an input signal being a modulated signal that is input to said power amplifier, or of a baseband waveform that is used to generate said modulated signal, for detecting an excess input signal according to a predetermined reference level, above which at least a portion of said input signal is defined as the excess input signal;
b) a power supply for indirectly supplying an operating voltage to said power amplifier; and
c) an analog control circuit, operating in combination with said power supply, for causing said power supply to supply a lower level of operating voltage being essentially constant and sufficient to effectively amplify input signals having a magnitude below said reference level, to said power amplifier, if no excess input signal is detected, and whenever an excess input signal is detected, to supply, to said power amplifier, a higher level of operating voltage that essentially tracks the magnitude of said excess input signal and being sufficient to effectively amplify input signals having a magnitude above said reference level.
20. Apparatus for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio, comprising:
a) a modulator for generating a modulated signal that is input to the power amplifier;
b) a baseband signal source for generating a baseband waveform that is input to said modulator;
c) a sampling circuit for continuously sampling the magnitude of said baseband waveform, for detecting an excess input signal according to a predetermined reference level, above which at least a portion of said baseband waveform is defined as an excess baseband signal;
d) a power supply for indirectly supplying an operating voltage to said power amplifier; and
e) an analog control circuit, operating in combination with said power supply, for causing said power supply to supply a lower level of operating voltage being essentially constant and sufficient to effectively amplify input signals having a magnitude below said reference level, to said power amplifier, if no excess input signal is detected, and to supply a higher level of operating voltage that essentially tracks the magnitude of said excess input signal and being sufficient to effectively amplify input signals having a magnitude above said reference level, to said power amplifier, whenever an excess input signal is detected.
3. A method for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio, comprising:
a) determining a reference level, above which at least a portion of the magnitude of an input signal being a modulated signal that is input to said power amplifier, or a baseband waveform that is used to generate said modulated signal, is defined as an excess input signal;
b) continuously sampling said magnitude of said input signal, for detecting an excess input signal;
c) supplying a lower level of operating voltage to said power amplifier, if no said excess input signal is detected, said lower level of operating voltage being sufficient to effectively amplify input signals having a magnitude below said reference level;
d) supplying a higher level of operating voltage to said power amplifier, whenever said excess input signal is detected, said higher level of operating voltage being sufficient to effectively amplify input signals having a magnitude above said reference level;
e) coupling an automatic gain control circuit to the input of said power amplifier, for controlling the magnitude of said input signal(s) prior to amplification;
f) whenever an excess input signal is detected, sampling said excess input signal; and
g) compensating changes in the gain of said power amplifier during the presence of said excess input signal by controlling the gain of said automatic gain control circuit, according to the samples of said excess input signal.
12. Apparatus for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio, comprising:
a) a sampling circuit for continuously sampling the magnitude of an input signal being a modulated signal that is input to said power amplifier, or of a baseband waveform that is used to generate said modulated signal, for detecting an excess input signal according to a predetermined reference level, above which at least a portion of said input signal is defined as the excess input signal;
b) a power supply for indirectly supplying an operating voltage to said power amplifier;
c) a first control circuit, operating in combination with said power supply, for causing said power supply to supply a lower level of operating voltage sufficient to effectively amplify input signals having a magnitude below said reference level, to said power amplifier, if no excess input signal is detected, and to supply a higher level of operating voltage being sufficient to effectively amplify input signals having a magnitude above said reference level, to said power amplifier, whenever an excess input signal is detected;
d) all automatic gain control circuit, coupled to the input of said power amplifier, for controlling the magnitude of said input signal(s) prior to amplification;
e) circuitry for sampling said excess input signal; and
f) a second control circuitry, for compensating changes in the gain of said power amplifier during the presence of said excess input signal by controlling tho gain of said automatic gain control circuit, according to the samples of said excess input signal.
2. A method according to claim 1, wherein the level of DC voltage, supplied to the power amplifier, is controlled, using the baseband waveform, by performing the following steps:
a) providing a modulator, fed by a baseband signal source that outputs said baseband waveform, for generating a modulated input signal to said power amplifier;
b) supplying a lower level of operating voltage to said power amplifier, if no excess baseband signal is detected, said lower level of operating voltage being sufficient to effectively amplify input signals, modulated with a baseband waveform having a magnitude below the reference level; and
c) supplying a higher level of operating voltage to said power amplifier, whenever an excess baseband signal is detected, said higher level of operating voltage being sufficient to effectively amplify input signals, modulated with a baseband waveform having a magnitude above said reference level.
4. A method according to claim 3, wherein the level of operating voltage is supplied to the power amplifiers by performing the following steps:
a) providing a lower voltage source for feeding said power amplifier whenever no excess input signal is detected;
b) providing a higher voltage source for feeding said power amplifier whenever an excess input signal is detected;
c) connecting the voltage supply contact of said power amplifier, to said lower voltage source through a first variable impedance, and to said higher voltage source through a second variable impedance;
d) whenever no excess input signal is detected, simultaneously controlling said first and said second variable impedances to be in their lowest and highest impedance states, respectively; and
e) whenever an excess input signal is detected, simultaneously controlling said first and said second variable impedances to be in their highest and lowest impedance states, respectively.
5. A method according to claim 3, wherein the level of operating voltage is supplied to the power amplifier by performing the following steps:
a) providing a first voltage source for feeding said power amplifier whenever no excess input signal is detected;
b) providing another voltage source for feeding said power amplifier whenever an excess input signal is detected;
c) connecting the voltage supply contact of said power amplifier, to said first voltage source through a variable impedance, and to said another voltage source through a voltage amplifier, said variable impedance being capable of presenting a low resistance to DC and high impedance for rapidly varying pulses;
d) whenever no excess input signal is detected, allowing said variable impedance to reach its lowest resistance; and
e) whenever an excess input signal is detected, allowing said variable impedance to reach its high impedance, and allowing said voltage amplifier to supply a voltage level, being higher than the voltage of said first voltage source, to said voltage supply contact of said power amplifier.
6. A method according to claim 4, wherein at least one of the variable impedances is a controllable impedance.
7. A method according to claim 4, wherein the variable impedance is an inductor or a diode.
8. A method according to claim 6, wherein the controllable impedance is a bipolar transistor or a FET.
9. A method according to claim 3, further comprising:
a) normalizing levels of operating voltage, supplied to said power amplifier, to corresponding predetermined levels of the excess input signal;
b) sampling the level of operating voltage supplied to said power amplifier;
c) generating an error signal by comparing between the sampled level with said excess input signal; and
d) using said error signal for operating a negative feedback loop for accurately controlling the operating voltage supplied to said power amplifier.
10. A method according to claim 3, further comprising:
a) normalizing levels of the excess input signal to corresponding predetermined levels of RF output signals, amplified by said power amplifier;
b) sampling the level of RF output signals, amplified by said power amplifier;
c) generating an error signal by comparing between the sampled level with said excess input signal; and
d) using said error signal for operating a negative feedback loop for accurately controlling the operating voltage supplied to said power amplifier.
13. Apparatus according to claim 12, comprising:
a) a lower voltage source for feeding said power amplifier whenever no excess input signal is detected;
b) a higher voltage source for feeding said power amplifier whenever an excess input signal is detected;
c) a first variable impedance connected between the voltage supply input of said power amplifier and said lower voltage source;
d) a second variable impedance connected between the voltage supply input of said power amplifier and said higher voltage source; and
wherein the first control circuit is configured for simultaneously controlling said first and said second variable impedances to be in their lowest and highest impedance states, respectively, whenever no excess input signal is detected, and to be in their highest and lowest impedance states, respectively, whenever an excess input signal is detected.
14. Apparatus according to claim 12, comprising:
a) a first voltage source for feeding said power amplifier whenever no excess input signal is detected;
b) another voltage source for feeding said power amplifier whenever an excess input signal is detected;
c) a variable impedance connected between a voltage supply contact of said power amplifier and said first voltage source, said variable impedance being capable of presenting a low resistance to DC and high impedance for rapidly varying pulses;
d) a voltage amplifier connected between the voltage supply contact of said power amplifier and said another voltage source, for supplying a voltage level, being higher than the voltage of said first voltage source, to said voltage supply contact of said power amplifier;
wherein the first control circuit is configured for controlling said voltage amplifier to supply said voltage level, being higher than the voltage of said first voltage source, to said voltage supply contact of said power amplifier, whenever no excess input signal is detected, and if said variable impedance is a controllable impedance:
for controlling said variable impedance to reach its high impedance value whenever an excess input signal is detected, and to reach its lowest resistance whenever no excess input signal is detected.
15. Apparatus according to claim 13, in which at least one of the variable impedances is a controllable impedance.
16. Apparatus according to claim 13, in which the variable impedance is an inductor or a diode.
17. Apparatus according to claim 16, in which the controllable impedance is a bipolar transistors or a FET.
18. Apparatus according to claim 12, wherein the sampling circuit is configured for sampling the level of operating voltage supplied to said power amplifier, the apparatus further comprising;
a) a comparator for generating an error signal by comparing between the sampled level of operating voltage supplied to said power amplifier, with the level of the excess input signal; and
b) a negative feedback loop for accurately controlling the operating voltage supplied to said power amplifier, by using said error signal.
19. Apparatus according to claim 12, wherein the sampling circuit is configured for sampling the level of RF output signals, amplified by said power amplifier, the apparatus further comprising:
a) a comparator for generating an error signal by comparing between the sampled level of RF output signals, amplified by said power amplifier, with the level of the excess input signal; and
b) a negative feedback loop for accurately controlling the operating voltage supplied to said power amplifier, by using said error signal.

The application claims the benefit of the U.S. Provisional Application No. 60/188,194, filed Mar. 10, 2000.

The present invention relates to the field of power amplifiers. More particularly, the invention relates to a method and apparatus for improving the efficiency of power amplifiers operating under large peak-to-average ratios, while eliminating the need for clipping signals having large peak amplitudes.

Modern communication systems, such as cellular systems employ power amplifiers in their basestations, in order to communicate with subscribers that are distributed in cells. These power amplifiers that are required to amplify Radio Frequency (RF) signals, such as signals used in communication systems that are required to transmit multiple signals, simultaneously. Multiple signals should be transmitted, for example, due to multiple users sharing the same frequency band, such as cellular systems that are operated in Code Division Multiple Access (CDMA) regimes. Another communication method that requires simultaneous transmissions employ, for example, a modulation format known as "multi-tone", or Orthogonal Frequency Division Multiplexing (OFDM), in which the signal from a single user is first subdivided. Each subdivision is then modulated by a multiplicity of staggered subcarriers. The modulated subcarriers are then added up, thus causing large peak excursions.

Conventional RF amplifiers required to simultaneously amplify RF signals that have large peak-to-average ratios, are costly and relatively inefficient (consuming much DC power). The reason for such inefficiency is that a power amplifier becomes efficient only during the occurrence of the peaks, i.e., when the instantaneous power output is large. However, during most of the time, the power output is only a small fraction of the power drain from the Direct Current (DC) power supply, resulting in low efficiency.

In order to reduce the average power loss, communication system designers use conventional techniques for reducing the peak to average ratio, based on clipping of the signal peaks. "Keeping noise mitigation for ODFM by decision-aided reconstruction" to Kim et al, IEEE Communications Letters, Vol. 3, No. 1, January 1999 and "Design considerations for multicarrier CDMA base station power amplifiers", to J. S. Kenney et al, Microwave Journal, February 1999, describe such techniques, which treat OFDM and multicarrier communications. It is also explained there that clipping considerably increases the undesired error rate of the system, and in some cases cause a partial spectral re-growth. Considerable effort is directed to mitigate the increase in the error rate while increasing the amount of clipping.

"Considerations on applying OFDM in a highly efficient power amplifier" to W. Liu et al, IEEE transactions on circuits and systems, Vol. 46, No. 11, November 1999, relates to the classical Envelope Elimination and Reconstruction (EER) for OFDM. "Device and circuit approaches for next-generation wireless communications" to P. Asbeck et al, Microwave Journal, February 1999, discloses similar features EER for OFDM, with sundry modifications for multicarrier transmission. However, all the above references depend on continuously varying power supplies for the envelope reconstruction or emphasis, which is difficult to achieve at large bandwidths and large peak to average ratios. Furthermore, EER techniques are mostly used for low-frequency modulation.

All the methods described above have not yet provided satisfactory solutions to the problem of improving the efficiency of power amplifiers operated under large peak-to-average ratios, while eliminating the need for clipping signals having large peak amplitudes.

It is an object of the present invention to provide a method and apparatus for improving the efficiency of power amplifiers operated under large peak-to-average ratios, while eliminating the need for clipping signals.

It is another object of the present invention to provide a method and apparatus for improving the efficiency of power amplifiers operated under large peak-to-average ratios, while eliminating spectral re-growth of unwanted sidebands.

It is still another object of the present invention to provide a method and apparatus for expanding the dynamic range of power amplifiers operated under large peak-to-average ratios.

Other objects and advantages of the invention will become apparent as the description proceeds.

The present invention is directed to a method for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio. A reference level is determined, above which at least a portion of the magnitude of an input signal being a modulated signal that is input to the power amplifier, or a baseband waveform that is used to generate the modulated signal, is defined as an excess input signal. The magnitude of the input signal is continuously sampled, for detecting an excess input signal. A lower level of operating voltage is supplied to the power amplifier, if no excess input signal is detected. The lower level of operating voltage is sufficient to effectively amplify input signals having a magnitude below the reference level. A higher level of operating voltage is supplied to the power amplifier, whenever an excess input signal is detected. The higher level of operating voltage is sufficient to effectively amplify input signals having a magnitude above the reference level.

Preferably, an automatic gain control circuit is coupled to the input of the power amplifier, in order to control the magnitude of the input signal(s) prior to amplification. Whenever an excess input signal is detected, the excess input signal is sampled. Changes in the gain of the power amplifier during the presence of the excess input signal are compensated by controlling the gain of the automatic gain control circuit, according to the samples of the excess input signal.

The level of operating voltage is supplied to the power amplifier by a lower voltage source for feeding the power amplifier whenever no excess input signal is detected and a higher voltage source for feeding the power amplifier whenever an excess input signal is detected. The voltage supply contact of the power amplifier is connected to the lower voltage source through a first variable impedance, and may be connected to the higher voltage source through a second variable impedance. Whenever no excess input signal is detected, the first and the second variable impedances may be simultaneously controlled to be in an appropriate low, and highest impedance states, respectively. Whenever an excess input signal is detected, the first and the second variable impedances may be simultaneously controlled to be in their highest and an appropriate low impedance states, respectively.

Preferably, the level of operating voltage is supplied to the power amplifier by using another voltage source for feeding the power amplifier whenever an excess input signal is detected. The voltage supply contact of the power amplifier is connected to the first voltage source through a variable impedance, and to the another voltage source through a voltage amplifier. The variable impedance can present a low resistannce to DC and high impedance for rapidly varying pulses. The variable impedance is allowed to reach an appropriate low resistance whenever no excess input signal is detected, and its high impedance whenever an excess input signal is detected. The voltage amplifier is allowed to supply a voltage level that is higher than the voltage of the first voltage source, to the voltage supply contact of the power amplifier, whenever an excess input signal is detected. At least one of the variable impedances may be an inductor or a diode, or a controllable impedance, such as a bipolar transistor or a FET.

Preferably, levels of operating voltage, supplied to the power amplifier, are normalized to corresponding predetermined levels of the excess input signal. The level of operating voltage supplied to the power amplifier sampled and an error signal is generated by comparing between the sampled level with the excess input signal. The error signal is used to operate a negative feedback loop for accurately controlling the operating voltage supplied to the power amplifier.

Alternatively, levels of operating voltage, supplied to the power amplifier, are normalized to corresponding predetermined levels of RF output signals, amplified by the power amplifier. The level of RF output signals, amplified by the power amplifier is sampled and an error signal is generated by comparing between the sampled level with the excess input signal. The error signal is used for operating a negative feedback loop for accurately controlling the operating voltage supplied to the power amplifier.

According to another aspect of the invention, the level of DC voltage, supplied to the power amplifier, is controlled, using the baseband waveform. A baseband signal source outputs the baseband waveform into a modulator, that generates a modulated input signal which is fed into the power amplifier. A reference level, above which at least a portion of the baseband waveform, is defined as an excess baseband signal is determined. The magnitude of the baseband waveform is continuously sampled, for detecting an excess baseband signal. A lower level of operating voltage is supplied to the power amplifier, if no excess baseband signal is detected. The lower level of operating voltage is sufficient to effectively amplify input signals, modulated with a baseband waveform of a magnitude below the reference level. A higher level of operating voltage is supplied to the power amplifier, whenever an excess baseband signal is detected. The higher level of operating voltage is sufficient to effectively amplify input signals that are modulated with a baseband waveform of a magnitude above the reference level.

The present invention is also directed to an apparatus for improving the efficiency and the dynamic range of a power amplifier operated with signals having a large peak-to-average ratio. The apparatus comprises a sampling circuit for continuously sampling the magnitude of an input signal, which may be a modulated signal that input to the power amplifier, or of a baseband waveform that is used to generate the modulated signal. The sampling circuit detects an excess input signal according to a predetermined reference level, above which at least a portion of the input signal is defined as an excess input signal; a power supply for indirectly supplying an operating voltage to the power amplifier; and a control circuit that operates in combination with the power supply, for causing the power supply to supply a lower level of operating voltage that is sufficient to effectively amplify input signals of a magnitude below the reference level, to the power amplifier, if no excess input signal is detected, and to supply a higher level of operating voltage that is sufficient to effectively amplify input signals of a magnitude above the reference level, to the power amplifier, whenever an excess input signal is detected.

The apparatus may further comprise:

a) an automatic gain control circuit, coupled to the input of the power amplifier, for controlling the magnitude of the input signal(s) prior to amplification;

b) circuitry for sampling the excess input signal; and

c) a control circuitry, for compensating changes in the gain of the power amplifier during the presence of the excess input signal by controlling the gain of the automatic gain control circuit, according to the samples of the excess input signal.

The apparatus may comprise:

a) a lower voltage source for feeding the power amplifier whenever no excess input signal is detected;

b) a higher voltage source for feeding the power amplifier whenever an excess input signal is detected;

c) a first variable impedance connected between the voltage supply input of the power amplifier and the lower voltage source;

d) a second variable impedance connected between the voltage supply input of the power amplifier and the higher voltage source; and

e) a control circuit for simultaneously controlling the first and the second variable impedances to be in an appropriate low, and highest impedance states, respectively, whenever no excess input signal is detected, and to be in their highest, and an appropriate low impedance states, respectively, whenever an excess input signal is detected.

Preferably, the apparatus comprises:

a) a first voltage source for feeding the power amplifier whenever no excess input signal is detected;

b) another voltage source for feeding the power amplifier whenever an excess input signal is detected;

c) a variable impedance connected between the voltage supply contact of the power amplifier and the first voltage source, the variable impedance being capable of presenting a low resistance to DC and high impedance for rapidly varying pulses;

d) a voltage amplifier connected between the voltage supply contact of the power amplifier and the another voltage source, for supplying a voltage level, being higher than the voltage of the first voltage source, to the voltage supply contact of the power amplifier;

e) a control circuit, for controlling the voltage amplifier to supply a voltage level, being higher than the voltage of the first voltage source, to the voltage supply contact of the power amplifier, whenever no excess input signal is detected, and if the variable impedance is a controllable impedance:

for controlling the variable impedance to reach its high impedance value whenever an excess input signal is detected, and to reach an appropriate low resistance whenever no excess input signal is detected.

At least one of the variable impedances of the apparatus may be an inductor or a diode, or a controllable impedance, such as a bipolar transistor or a FET. The apparatus may further comprise:

a) a sampling circuit for sampling the level of operating voltage supplied to the power amplifier;

b) a comparator for generating an error signal by comparing between the sampled level of operating voltage supplied to the power amplifier, with the level of the excess input signal; and

c) a negative feedback loop for accurately controlling the operating voltage supplied to the power amplifier, by using the error signal.

The apparatus may further comprise:

a) a sampling circuit for sampling the level of RF output signals, amplified by the power amplifier;

b) a comparator for generating an error signal by comparing between the sampled level of RF output signals, amplified by the power amplifier, with the level of the excess input signal; and

c) a negative feedback loop for accurately controlling the operating voltage supplied to the power amplifier, by using the error signal.

Alternatively, the apparatus may further comprise:

a) a modulator for generating a modulated signal that is input to the power amplifier;

b) a baseband signal source for generating a baseband waveform that that is input to the modulator;

c) a sampling circuit for continuously sampling the magnitude of the baseband waveform, for detecting an excess input signal according to a predetermined reference level, above which at least a portion of the baseband waveform is defined as an excess baseband signal;

d) a power supply for indirectly supplying an operating voltage to the power amplifier; and

e) a control circuit, operating in combination with the power supply, for causing the power supply to supply a lower level of operating voltage being sufficient to effectively amplify input signals having a magnitude below the reference level, to the power amplifier, if no excess input signal is detected, and to supply a higher level of operating voltage being sufficient to effectively amplify input signals having a magnitude above the reference level, to the power amplifier, whenever an excess input signal is detected.

The above and other characteristics and advantages of the invention will be better understood through the following illustrative and non-limitative detailed description of preferred embodiments thereof, with reference to the appended drawings, wherein:

FIGS. 1A and 1B schematically illustrate the waveform of the input signal to the power amplifier and the desired waveform of the supply voltage to the power amplifier, respectively, according to a preferred embodiment of the invention;

FIG. 2A is a block diagram of the basic circuit for controlling the supply voltage to the power amplifier, according to a preferred embodiment of the invention;

FIG. 2B is a block diagram of a circuit for controlling the enhanced supply voltage to the power amplifier by feeding back part of the enhanced voltage, according to a preferred embodiment of the invention;

FIG. 2C schematically illustrates computed simulated results of the supplied voltage with and without Excess Signal (ES) feedback, according to a preferred embodiment of the invention;

FIG. 3 is a block diagram of a circuit for controlling the supply voltage to the power amplifier when there is access to baseband signals, according to a preferred embodiment of the invention; and

FIG. 4 is a block diagram of a circuit for controlling the supply voltage to the power amplifier with an output control, according to a preferred embodiment of the invention.

FIGS. 1A and 1B schematically illustrate the waveform of the input signal to the power amplifier and the desired waveform of the supply voltage to the power amplifier, respectively, according to a preferred embodiment of the invention. The waveform ven(t) in FIG. 1A illustrates the positive envelope of an input RF signal, input to the power amplifier. An Excess Signal (ES) occurs when the level of the Signal Envelope (SE) exceeds a predetermined Reference Level (L) defined by the system designer. The present invention provides a circuitry called Voltage Enhancement (VE) Circuitry (VEC), described further below, that causes the supply voltage to the RF amplifier to have the desired waveform, as shown in FIG. 1B: The supply voltage normally remains in a constant value, +Bc, (the subscript C for "conventional") and is varied (enhanced) only during the anomalous periods when the level of the input signal is higher than the predetermined Reference Level (L) (i.e., there is an ES). The resulting enhanced voltage (EV) waveform is a close replica of the ES waveform, as indicated by comparing between FIGS. 1A and 1B.

FIG. 2A is a block diagram of the basic circuit for controlling the supply voltage to the power amplifier, according to a preferred embodiment of the invention. The circuit 200 comprises an Excess Envelope Sensor (EES) 201, a VEC 202, RF stages 209, 204 and an input coupler at point 14. The RF power amplifier 204 is designed such that when there is no excess signal ES at point 12, the DC supply +Bc is sufficient to amplify the modulated RF signal at point 25 with the required fidelity. However, when signal 25 reaches peak values, the RF power amplifier 204 would be saturated if the voltage +Bc is supplied. Such peaks are sensed by the EES 201 that outputs the excess signal ES at point 12 resulting from these peaks, to the VEC block 202 which, in turn, appropriately enhances the voltage vout (t) (that appears at point 15), fed to the RF power amplifier 204. This is indeed, the enhanced voltage EV, introduced in FIG. 1B. Therefore, the RF power amplifier 204 with the enhanced supply voltage remains unsaturated when the input RF signal peaks occur, and the amplification remains adequate.

The EES 201 detects an ES by sampling the RF signal at the input 14, and comparing the sample that appears at input 11 of EES 201 to the reference level L that appears at input 13 of EES 201. EES 201 outputs the excess signal (ES) at point 12. The ES is then input to the VEC block 202, which is configured such that it outputs the desired supply voltage vout (t) (shown in FIG. 1B) at point 15, to the RF amplifier 204. During normal periods when there is no ES at point 12, the Analog Power Valve (APV) 203 is essentially in cut-off and the VE LOAD block 205 introduces a low DC resistance. Thus, the DC voltage +Bc at point 16 is fully applied to the RF amplifier 204. In this state, vout=+Bc, as indicated also in FIG. 1B above. On the other hand, the VE LOAD block 205 provides a high impedance to a positive pulse, such as a voltage enhancement pulse that is supplied by the Analog Power Valve (APV) 203 when the latter is excited by an ES. According to a preferred embodiment of the invention, the VE LOAD block 205 can be implemented using either an RF choke L1, or a diode with its anode connected to a voltage +Bc, or a voltage controlled transistor (such as a Field-Effect-Transistor (FET), or a bipolar transistor).

The APV block 203 can be implemented as a transistor, for example a Field-Effect Transistor (FET) Q1, or a bipolar transistor, and be conveniently biased to be normally in the cut-off state, except when excited by the output of the Excess Signal Amplifier (ESA) 206. The APV block 203 may be powered from a separate DC voltage source, Bv. The optional Excess Signal Shaper (ESS) 207 that translates the ES to the input of ESA 206, is a memory-less, monotonic non-linearity. The purpose of ESA 206 is to output, at point 23, an altered shape of the Excess Signal that appears at point 12, in order to counteract possible non-linearities incurred in the APV block 203 and in the characteristics of the RF amplifier 204.

According to a preferred embodiment of the invention, the excess signal (ES) output at point 12 may also be used to adjust the overall gain of the RF chain during effectuation of the voltage enhancement (VE), for improved fidelity. Such option is shown by the dotted lines in FIG. 2A. The ES is appropriately conditioned by the AGC Shaper (AGCS) block 208, and then applied to control the gain of the instantaneous automatic gain control (IAGC) stage 209. The AGCS block 208, very much like the ESS 207, is also a memory-less monotonic nonlinearity. The concept behind the two shapers ESS 207, and AGCS 208 is the following: Basically, the voltage enhancement of the RF amplifier 204 is intended to increase its dynamic range. However, such VE will, to a certain extent, also increase the gain of the RF amplifier 204. The IAGC stage 209 is used to compensate the gain changes by decreasing its own gain accordingly. The transfer functions of the ESS 207 and the AGCS block 208 can be adjusted for linearity of gain, while the dynamic range is extended during the voltage enhancement period.

FIG. 2B is a block diagram of a circuit for controlling the enhanced supply voltage to the power amplifier by feeding back part of the enhanced voltage, according to a preferred embodiment of the invention. By using this option, it is possible to obtain better fidelity than by using the Excess Signal Shaper (ESS) block 207 alone, as shown in FIG. 2A hereinabove. A comparator 210 compares the output voltage vout (t) that appears at point 15, with the ES that appears at point 12. The difference voltage that appears at point 32 is fed into the VEC 202. This constitutes a modified Feed Back VEC (FB-VEC) indicated by the reference numeral 211 in FIG. 2B. Depending on the plurality of said difference voltage, the voltage amplification of the VEC 202 will either be increased or decreased, until the EV will track the ES.

FIG. 2C schematically illustrates computer-simulated results of a conventional amplifier and of the FB-VEC of FIG. 2B, according to a preferred embodiment of the invention. The upper graph shows the waveform of the envelope of the input signal to the RF amplifier 204 that is composed of nine channels of a CDMA signal (scaled by 3.6). The other graphs show the envelope of the output from the RF amplifier 204. The middle graph shows a conventional situation, when the VEC is disabled and only the voltage +Bc is supplied. Severe distortion of outputs above 80 Volts is noticeable. The lower graph shows the situation when the FB-VEC 211 (shown in FIG. 2B) is operated. In the lower graph, the fast tracking of the change in the envelope amplitude above values of 80 Volts is noteworthy.

FIG. 3 is a block diagram of a circuit for controlling the supply voltage to the power amplifier when there is access to baseband signals, according to a preferred embodiment of the invention. The circuit 300 employs a VEC block 301, which may be either the basic VEC 202 without feedback (shown in FIG. 2B), or the FB-VEC (shown in FIG. 2B). The circuit 300 is implemented with access to the amplitude value of the Base Band Signal Source (BBSS) 302, at point 31. The RF power amplifier 204 should amplify RF signals with large peaks above its average value, as obtained from the Base Band Signal Source 302. The BBSS 302 outputs complex signals at point 34, which are input to an appropriate modulator 303 that is also fed by an RF sinewave from an RF oscillator 304. The BBSS 302 feeds the amplitude information that appears at point 31 into the Voltage Slicer 305. The Voltage Slicer 305 performs the same operation on a Base Band Signal, as the EES block 201 performs on an input RF signal: It extracts an excess signal ES at point 32 when the amplitude at point 31 exceeds the reference level L. The operations that follow are exactly as shown in FIG. 2A above.

FIG. 4 is a block diagram of a circuit for controlling the enhanced supply voltage to the power amplifier by feeding back part of the RF amplifier output signal, rather than part of the EV, as shown in FIG. 2B. The circuit 400 is a refinement of the FB-VEC block 211, shown in FIG. 2B. Comparator 401 compares the output of the EES 201 with the output of an additional EES 402, that is coupled to the output (point 48) of the RF power amplifier 204, by a coupler 212. As shown in FIG. 2B above, the difference voltage at point 32, that appears at the output of the comparator 401, is fed into the VEC block 202. The fact that in this implementation the feedback loop includes also the RF power amplifier 204 is advantageous, since circuit 400 can potentially correct non-linearities of the RF power amplifier 204, as well.

The above examples and description have of course been provided only for the purpose of illustration, and are not intended to limit the invention in any way. As will be appreciated by the skilled person, the invention can be carried out in a great variety of ways, employing more than one technique from those described above, all without exceeding the scope of the invention.

Bar-David, Israel

Patent Priority Assignee Title
10511264, Nov 24 2014 GEPSTEIN, OFER Adaptive impedance power amplifier
10797916, Aug 08 2016 Molex, LLC EHF receiver architecture with dynamically adjustable discrimination threshold
6735419, Jan 18 2001 Google Technology Holdings LLC High efficiency wideband linear wireless power amplifier
6937094, Nov 22 2002 Intel Corporation Systems and methods of dynamic bias switching for radio frequency power amplifiers
7038539, May 06 2003 TAHOE RESEARCH, LTD RF amplifier employing active load linearization
7091777, Sep 30 2002 Lucent Technologies Inc. Controller for an RF power amplifier
7339426, Mar 19 2004 TAHOE RESEARCH, LTD High efficiency linear amplifier employing dynamically controlled back off
7348847, Apr 28 2005 SiGe Semiconductor Inc. Integrated implementation of a collector boost scheme and method therefor
7362818, Aug 30 2001 Apple Inc Amplitude and phase comparator for microwave power amplifier
7366482, Oct 07 2003 MATSUSHITA ELECTRIC INDUSTRIAL CO , LTD Transmission device, transmission output control method, and radio communications device
7440733, Apr 09 2004 TAHOE RESEARCH, LTD Constant gain nonlinear envelope tracking high efficiency linear amplifier
7466195, May 18 2007 QUANTANCE, INC Error driven RF power amplifier control with increased efficiency
7570709, Mar 08 2001 Siemens Aktiengesellschaft Automatic transmit power control loop with modulation averaging
7728663, Jun 22 2006 SiGe Semiconductor Inc. Integrated implementation of a voltage boost follower and method therefor
7761065, Feb 03 2006 QUANTANCE, INC RF power amplifier controller circuit with compensation for output impedance mismatch
7777566, Feb 05 2009 QUANTANCE, INC Amplifier compression adjustment circuit
7782132, Sep 26 2006 Qualcomm Incorporated Method and apparatus for improving the performance of MIMO wireless systems
7782134, Sep 09 2008 QUANTANCE, INC RF power amplifier system with impedance modulation
7783269, Sep 20 2007 QUANTANCE, INC Power amplifier controller with polar transmitter
7856105, Mar 09 2006 Andrew LLC Apparatus and method for processing of amplifier linearization signals
7868700, Nov 28 2006 Qualcomm Incorporated Method and apparatus for reducing current consumption of MIMO systems
7869542, Feb 03 2006 QUANTANCE, INC Phase error de-glitching circuit and method of operating
7876853, Feb 03 2006 Quantance, Inc. Phase error de-glitching circuit and method of operating
7899417, Jul 20 2006 Qualcomm Incorporated Method and apparatus for increasing the efficiency of low power amplifiers
7917105, Feb 03 2006 Quantance, Inc. RF power amplifier controller circuit with compensation for output impedance mismatch
7917106, Feb 03 2006 QUANTANCE, INC RF power amplifier controller circuit including calibrated phase control loop
7932780, May 21 2006 Qualcomm Incorporated Method for implementation and parameter settings of a voltage enhancement circuit for amplifiers as an integrated circuit (IC)
7933570, Feb 03 2006 QUANTANCE, INC Power amplifier controller circuit
8014735, Nov 06 2007 QUANTANCE, INC RF power amplifier controlled by estimated distortion level of output signal of power amplifier
8018277, Sep 09 2008 QUANTANCE, INC RF power amplifier system with impedance modulation
8022761, May 18 2007 Quantance, Inc. Error driven RF power amplifier control with increased efficiency
8032097, Feb 03 2006 QUANTANCE, INC Amplitude error de-glitching circuit and method of operating
8050638, Sep 20 2007 Quantance, Inc. Power amplifier controller with polar transmitter
8095090, Feb 03 2006 QUANTANCE, INC RF power amplifier controller circuit
8107902, Nov 28 2006 Qualcomm Incorporated Method and apparatus for optimizing current consumption of amplifiers with power control
8179994, Feb 03 2006 Quantance, Inc. Phase error de-glitching circuit and method of operating
8193860, Nov 21 2006 Qualcomm Incorporated Method and apparatus for automatically controlling an XNN® enhancement circuitry feeding a power amplifier
8208876, Feb 03 2006 QUANTANCE, INC Amplifier compression controller circuit
8238853, Feb 03 2006 Quantance, Inc. Amplitude error de-glitching circuit and method of operating
8260225, Feb 03 2006 Quantance, Inc. Power amplifier controller circuit
8274328, Nov 18 2009 Fujitsu Limited Amplifying apparatus
8340604, Feb 03 2006 Quantance, Inc. RF power amplifier controller circuit including calibrated phase control loop
8417199, Jul 23 2010 MOTOROLA SOLUTIONS, INC Method and apparatus for improving efficiency in a power supply modulated system
8483633, Jul 23 2010 MOTOROLA SOLUTIONS, INC Method and apparatus for alarming in a power supply modulated system
8536940, Mar 02 2009 RPX Corporation Method for amplifying a signal by a power amplifier, power amplifier system, device, computer program product, and digital storage medium thereof
8611835, May 21 2006 Qualcomm Incorporated Method and apparatus for sensing the envelope of high level multi frequency band RF signals
8718581, Nov 28 2005 Qualcomm Incorporated Method and apparatus for optimizing current consumption of amplifiers with power control
8754707, Oct 24 2012 Qualcomm Incorporated Boost converter control for envelope tracking
8866547, Jan 28 2013 Qualcomm Incorporated Dynamic headroom for envelope tracking
8908795, Oct 14 2011 Samsung Electronics Co., Ltd. Apparatus and method for calibration of supply modulation in transmitter
8981846, Mar 17 2006 SNAPTRACK, INC Joint optimisation of supply and bias modulation
8988059, Jan 28 2013 Qualcomm Incorporated Dynamic switch scaling for switched-mode power converters
9124231, Jan 28 2013 Qualcomm Incorporated Soft turn-off for boost converters
9225289, Mar 23 2014 PLOTNIK, ELI Method and apparatus for partial envelope tracking in handheld and wireless computing devices
9306520, Jan 28 2013 Qualcomm Incorporated Reverse current prevention
9356512, Jul 29 2013 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LIMITED Envelope tracking power supply with direct connection to power source
9442503, Jan 28 2013 Qualcomm Incorporated Negative current sense feedback for reverse boost mode
9537450, Jan 28 2013 Qualcomm Incorporated Dynamic headroom for envelope tracking
9601999, Jan 28 2013 Qualcomm Incorporated Dynamic switch scaling for switched-mode power converters
Patent Priority Assignee Title
2210028,
5142240, Dec 27 1989 Mitsubishi Denki Kabushiki Kaisha Amplifier circuit with correction of amplitude and phase distortions
5420536, Mar 16 1993 Victoria University of Technology Linearized power amplifier
5442317, Nov 10 1992 MOTOROLA SOLUTIONS, INC Switching regulator and amplifier system
5745526, Dec 15 1994 Nokia Mobile Phones Limited Radio transmitters and methods of operation
5883927, Jul 31 1996 MONUMENT BANK OF INTELLECTUAL PROPERTY, LLC Digital wireless telecommunication device for reduced interference with hearing aids
5886575, Sep 30 1997 Google Technology Holdings LLC Apparatus and method for amplifying a signal
5898342, Jan 20 1998 SAMSUNG ELECTRONICS CO , LTD Power amplifier arrangement and method for data signal interface
5929702, Nov 28 1997 Google Technology Holdings LLC Method and apparatus for high efficiency high dynamic range power amplification
6028486, Oct 07 1997 Telefonaktiebolaget LM Ericcson Method and apparatus for reducing power dissipation in multi-carrier amplifiers
6175372, Jan 03 1995 Microsoft Technology Licensing, LLC Method for estimating the memory required for scan conversation of a glyph
EP1041712,
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Jan 05 2012PARAGON COMMUNICATIONS LTD Qualcomm IncorporatedASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS 0276520235 pdf
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